Process for manufacturing lithium base greases



Aug. 27,1946. A. R. BAx Em.

PROCESS FOR MANUFACTURING LITHIUM BASE GREASES Filed Dem 21, 1943 v Patented Aug. 27, 1946 UNITED vPROCESS FOR MANUFACTURING LITHIUM BASE GREASES Alfred R. Bax, Laurel Springs,` Harry F. Kielhorn, Oaklym,y and William E. Forney, Merchantville, N. J., assignors to Cities Service Oil Company, New York, N. Y., av corporation of Pennsylvania y Applicaunn pembef 21, 1943. semi No. 515,100 11 claims. (c1. 25a-3) This invention relates to improvements 'in the manufacture of greases and more Particularly to the manufacture of lithium base greases.

Lithium base greases are of particular interest because lithium soaps give greases which have good lubricating properties at extremely low temy peratures o f the order of minus 100 F. At the same time the greases made from lithium soaps are also useful at temperatures of the order of approximately 300 F. Thiswide range of utility is especially advantageous in the lubrication of aircraft and other equipment which must be operated at ordinary temperatures aswell as at extremely low temperatures Aat which other greases become stii and hard and fail to lubricate.

In the manufacture of lithium base greases a cnumber of diiiiculties have been encountered which are not common to the manufacture of sodium and other greases. For example, no way has been developedfor the manufacture of la. lithium base grease with Pennsylvania type oils without the use of other materials. The reason for this is not understood since satisfactory greases have been made with Coastal type oils of a wide range of viscosity. Furthermore, some of the greases made with Pennsylvania oils, lithium soap and stearic acid, for example, were not Water-repellent, whereas the grease made with a Coastal oil and a lithium soap was Water-repellent. Other diiliculties have been encountered in the heating of the grease mixture, since excess or prolonged heating and excessive agit-ation at high temperatures, destroy the tackiness and water-repellent properties of the grease. The maintenance of the grease at the maximum heating temperature for an appreciable length of time destroys its grease-like properties.

'I'he 'primary object of the present invention is to provide improved method of manufacturing greases by which various factors are controlled and coordinated to produce a satisfactory grease.

A further object'of the invention is to provide an improved process for the successful manufacture of lithium base greases andl which overcomes the various special difiiculties encountered Ain the use of lithium soaps.

y etc., passing the resulting mixture in a confined stream of narrow cross-section and of great length through a heating zone in which the mixture is raised to a nnal temperature of from about 400? F. to about 450 F., depending on type of final product desired, maintaining the material at the inal temperature for not more than a few minutes, and then quickly cooling the -gzrease in thin layers down to ordinary tempera` ures.

The improved process of the present invention also includes other features such as the simultaneous working and heating of the grease mixture in the confinedy stream of restricted cross section.

The present invention, together with its various features and advantages, will be apparent to those skilled in the art from the following more detailed description thereof,- taken in connection withthe accompanying drawing and examples.

In the drawing:

The single figure is a diagrammatic view show'- ing. an apparatus particularly adapted for carrying out the improved process.

Referring to the drawing, a preferred form of the improved process ofthe present invention will be illustrated in connection with the manufacture of a batch of 4,000 pounds of a lithium base grease from 600 steam refined Pennsylvania lubricating stock. The constituents going into this batch of grease comprised 458 gallons ofthe lubricating oil stock, 88 pounds of aluminum tristearate, 440 pounds of lithium stearate, 40 pounds of polyisobutene having a molecular weight of about 20,000, andvtben pounds of tributyl phosphite as an oxidation inhibitor. The process is started by charging the 440 pounds of lithium stearate and 40 gallons of the oil into a steam jacketed mixing kettle I0 in which these ingredients are simultaneously mixed and heated to a temperature of 150-200 F., and prefer ably to about 170 F. The ou may be run into the kettle l0 through a feed line I2 While the lithium stearate is dumped in .by any suitable means. At the same time 229 gallons of the oil and the 88 pounds of aluminum tristearate is introduced into a second steam jacketed kettle I4, the oil being run in through a supply line I6. 'Ihe mixture in the kettle I4 is agitated thoroughly while heating it to a temperature of 270 F. by means of the steam jacket. After this temperature is reached in the kettle I4, the remaining oil, 189 gallons, the 10 pounds of tributyl phoshite, and the 40 pounds of polyisobutene are then dumped into the kettle Il and thoroughly agitated with the aluminum stearate mixture therein.

The lithium stearate mixture in the kettle I is now withdrawn through a line I8 and forced by means of a pump therein into the kettle I4 where it is quickly incorporated into the alumil num stearate mixture. The resulting slurry at va temperature of about 150-200 F. is withdrawn further processing equipment in a substantially continuous manner. The mixture is withdrawn from the kettle 22 through a line u and forced by means of a pump therein into and through along heating coil 26 of small diameter mounted in an oil bath in a long cylindrical reaction heater 28. The mixture is pumped under pressure through the small ycoil 26 and simultaneously heated and worked therein as it is forced through the coil. In the apparatus represented in the drawing the coil 26 comprised 800 feet of inch pipe mounted in an oil bath held at a temperature of approximately 440 F. The grease slurry from the kettle 22 was pumped through the coil at a rate of 10 to 15 pounds per minute and heated to a final temperature of about 435 F. One important aspect of the heating is the control of the temperature and the throughput so that the grease slurry is simultaneously heated and worked for approximately three minutes in the temperature range of from about 430 to 435 F.

The grease reaching the end of the outlet of the coil 26 is conducted through a transfer line 30 into a hot receiving tank 32 from which the' hot grease is picked up by a chilled steel cylinder 34 and instantly chilled to a temperature of from .70 to 100 F., depending upon the temperature of the available cooling water. The grease congeals on the chilling drum 34, and during the rotation of the drum itis removed by a scraper 36 and passed by means of a chute 38 into a receiver 40. Quick and almost instantaneous chilling of the hot grease from the high temperature of about`435 F. to at least 100 F., is extremely important in the production of a stable plastic grease. l i

The grease discharged from the heating coil .'26 is maintained at approximately the final desired temperature right up to the instant of chilling, by providing a jacket 42 around the greater portionof the transfer line 30, the jacket being filled with the hot oil from the reaction heater 28. Furthermore,l the hot oll from the jacket 42 is used to maintain the temperature of the hot lgrease in the receiving tank 32, which is provided jwith `a jacketed bottom 44 as indicated in the drawing. The hot oil is drawn from the jacket 42 through aline 46 into oneend of the jacket 44, withdrawn from the opposite end of the jacket 44 and conducted by means of a return pipe 43 and a pump 50 back into the chamber 28 at the opposite end of the jacket 42. The chamber 28 (of the shell still type) is provided with the' usual fire box mounting 52 and may be heated by oil orfgas burners as indicated.

The apparatus as shown may be operated substantially continuously by making up the lithium and aluminum soap mixtures separately in the kettles I0 and I4 `and using the large charging kettle 22 to maintain a continuous supply for the coil-heating-and-working operation. The pipe lines 20 and 24 are,provlded .with valves and a bypass line 54 by which the slurry may be supplied to the pump inthe line. 24 directly from the kettle I4. It is therefore possible to use the kettles I4 and 22 alternately, and provision may be made for dumping the contents of kettle I0 into the kettle 22.

The handling of the lithium stearate or other lithium soap is an extremely sensitive matter, and itis extremely important that the grease be nished as soon as reasonably possible after the lithium s tearate slurry is mixed with the aluminum stearate slurry. However, the mixing procedure described above may be varied and avoid the use of the kettle I0 by first making up a slurry of al1 of the ingredients except the ylithium stearate in the kettle I4, and then at the last moment dump in the lithium stearate, thoroughly incorporating it in the slurry and then charge it to the heating and working coil 26 or to the charging kettle 22.

The chilling drum 34 which is mounted so that it dips in the grease in the container 32 may be rotated by any suitable means such as a drive belt or chain and pulley 56. Cooling water is supplied to the drum 34 through a line 58 and withdrawn therefrom through a line 80. The

rotation of the drum 314 is maintained suin- Penetration (ASTM) 270 Water absorption 40% Melting point 381 F. Navy beater test satisfactory Navy torque test satisfactory ing coil of small diameter and great length provides an effective means for controlling the heating and Working of the grease. While the process is preferably adapted for the manufacture of lithium base greases, it may be used in the manufacture of known greases by the use of predetermined proportions of the desired metal soap or soaps and lubricating oil stocks. Lithium base greases may be made with'Pennsylvania lubricating oil stocks by the addition of aluminum soaps as described in the above example or by replacing the aluminum soap with stearic acid. However, the grease made with stearic acid-in place of aluminum soap is not water repellent. In the use of aluminum soaps, for example the monodior' In the foregoing example, mention is made of the use 4of an isobutylene polymer which was used to increase the tackiness and adherent properties of the grease. Other elastic polymers such as rubber latex, gum rubber, "Paratac a polymer similar to the polyisobutylene, chlorinated rubber, butyl rubber, buna rubber, and other elastic organic compounds may be used. Usually about 0.5% to 1% oi' such material is satisfactory. The butylene polymer such as polymerized isobutylene may have a molecular weight of from about 8000 to about 25,000. In using "Paratac the proportion necessary was only about half that of the polyisobutylene used in the illustrative example. v

The proportions oi' lithium stearate and alu'- minum stearate in the grease may vary somewhat according to the characteristics desired for the final product, but theratio of aluminum stearate to lithium stearate should be about 2% to 10%. For a dropping point oi' about 375 F.,

11% of lithium stearate and 2.2% oi! aluminum stearate were found necessary when using the 600 steam reiined Pennsylvania lubricating oil. Other lithium and aluminum soaps may be used.

In the manufacture of various types of greases or greases for various purposes, the temperature conditions in the apparatus may be varied. For

example, the temperature in the kettle M may 30 of an anti-oxidant and a small proportion of an vary from 250 F. to 300 F., while the oil bath in the cylindrical reaction heater 28 may vary from about 400 F. to 450 F. The iinal temperature to which the grease is heated in the coil 26 may also vary from about 400 F. to 450 F. and the reaction time changed by varying the throughput. trated in connection with a specific example, it will be understood that both the penetration and the melting point of the grease may be varied according to the type of greasedesired. A suitable lithium base grease may have a dropping point of from 375 F. to 395 F.

It is to be understood that the invention is not Mlimited to the specic example given but'| that various conditions such as the reaction time may be changed in accordance with oil stocks and soaps employed. as would be apparent to one skilled in the art.

Having thus described the invention, what is claimed as new is:

1. The method of manufacturing a lithium base 1 grease comprised mostly of a Pennsylvania 1usoap slurry and immediately passing the mixture through along heating coil of relatively small diameter in which the mixture is simultaneously heated and worked, heating the mixture in the final stages of the heating operation for a period of about three minutes in the temperature range of 430 to 440 F., discharging the resulting grease mixture from the heating coil and instantly chill-- ing the grease in very thin layers to a temperature of 100 F. or vbelow to produce a stable'homogeneous lithium base grease.

2. The method as defined by claim 1 in which a portion of the lubricating oil is mixed with a small proportion of an oxidation inhibitor and While the inventionhas been illusf a small proportion of an elastic polymer and which this mixture is incorporated in the aluminum soap slurry.

3. The method as dei-ined by claim l in which the hot grease is discharged from the heating 4. The method as defined by claim 1 in which the grease in the heating coil is heated by a bath of oil surrounding the coil and maintained at a temperature of about 445 F.

5. The method of manufacturing a lithium 15 base grease, which comprises forming a slurry of a lithium soap and a Coastal lubricating oil stock in the desired proportions for making a grease, introducing the slun'y into a long heating coil of small diameter and forcing the slurry therethrough at a rate adapted to give it a. thorough working, simultaneously heating the slurry t a iinal temperature of 40o-450 F. at a rate such that it is held within that range for a maximum period of about 3 minutes, and immediately chilling the mixture to a temperature of 100 F. or lower by picking up thin layers of it on a chilled roll.

6.' The method as deilned by claim 5 in which the original slurry contains a small proportion elastic polymer.

7. The method of manufacturing a lithium base grease, which comprises forming a slurry of an aluminum soap and a lubricating oil stock at a temperature of from 250 to 300 F., forming 40 through a long heating coil of small diameter in which the mixture is simultaneously worked and vprogressively raised in temperature to from 400 to 450 F., said heating being carried out at such a rate that the slurry is held within said iinal temperature range for a maximum of about three minutes, and quickly chilling the grease mixture in very thin layers to a temperature of 100 F. or below after it reaches said temperature of 400 to 450 F.

5o s. The method as defined by claim 'z in which approximately 11% of lithium soap and 2.2% of aluminum soap are used, the remaining percentage of the mixture being almost. entirely lubricating oil stock.

9. The method of manufacturing a stable plaslong heating coil of small diameter and forcing the slurry therethrough at a rate adapted to give a thorough working of. the slurry while it is simultaneously heated and raised in temperature to the desired iinal temperature, heating the slurry to a. final temperature adapted to produce a stable grease, and within a few minutes after it has reached such final temperature quickly chilling the grease mixture in thin layers to a low temperature of approximately 100 F. or lower.

10. The method of manufacturing a lithium at a temperature of from 150 to 200 F., mixing an aluminum soap and a temperature of 100 F. or less.' 11. The method of manufacturing a; lthium base grease which comprises forming a slurry of alubricatingoil at a temperature 'of from 250 to 300 F., separately forms ing a slurry of a lithumsoap and a lubricating oil stock at a temperature of from 150 to 200 F.,

` Y the aluminum soap slurryT passing `soap slurry and lithium the resulting mixture in a conned stream of narrow cross section through a heating zone in which the mixture is rapidly heated to a temperature of from, 400 to 450 F.,

and quickly chilling perature of 100 F. utes after it has reac to 450 F.

the grease mixture to' a, temor below within a few milihed said temperature of 400 mun R. BAX. HARRY'F. mELHoRN. WILLIAM E. FORNEY. 

